1. Field of the Invention
The present invention relates to a microscope system and, more particularly, to a microscope system capable adjusting the thickness of an optical sectioned image.
2. Description of the Related Art
Fluorescence microscopes are used widely in various fields including the medical and the biological field for detecting proteins and genes marked with fluorescent markers. Recently, multiple fluorescence detection that observes a specimen dyed with a plurality of fluorescent dyes and a specimen expressing a plurality of fluorescent proteins has become a powerful tool for the analysis of genes and intracellular structures.
A laser confocal microscope among fluorescence microscopes, in particular, differs from ordinary microscopes; the laser confocal microscope forms an image by detecting fluorescent light emitted from a point on which a laser beam is focused, removing fluorescent light emitted from parts other than the part at the focal point or scattered light with a pinhole screen placed in front of a detector. Thus, a high-contrast image of only a part at the focal point, i.e., an optical sectioned image, can be obtained.
A recently marketed laser microscope includes a detector, and a screen disk disposed in front of the detector and provided with a plurality of pinholes respectively having different diameters. The screen disk is turned to use the pinholes having the different diameters selectively. Another laser microscope has a variable-pinhole screen provided with a variable pinhole whose diameter can selectively be determined. The user of the laser microscope selects an optimum diameter for the pinhole according to the condition and shape of the specimen or according to the quantity of fluorescent dyes contained in the specimen or the amount of the fluorescent protein expressed by the specimen to adjust the thickness of an optical sectioned image of the specimen optionally.
A fringe projection method is a means for obtaining an optical sectioned image disclosed in Jpn. Pat. No. 3066874 (Patent document 1) The stripe projection method projects a light beam on a grating or the like, illuminates a specimen with a bright-and-dark periodic optical pattern having alternate arrangement of bright and dark parts formed by the grating, and takes a photograph of the thus illuminated specimen with a camera. A plurality of images obtained by using a plurality of bright-and-dark periodic optical patterns having different phases are processed, and periodic patterns are removed to obtain an optical sectioned image of a desired part.
Since the stripe projection method disclosed in Patent document 1 uses the grating for forming the bright-and-dark pattern, intervals between the elements of the periodic pattern is entirely dependent on the grating constant of the grating. Consequently, the thickness of the optical sectioned image cannot freely be adjusted according to the condition and shape of the specimen or according to the amount of fluorescent dyes contained in the specimen or the amount of expressed fluorescent proteins during observation. Such a problem may be solved by selectively using a plurality of gratings respectively having different grating constants. However, the optical system must be readjusted every time the grating is changed and hence it is difficult to change the grating quickly during observation of the specimen. Although the phase of the bright-and-dark pattern is shifted by moving the grating, an error in distance by which the grating is moved causes an error in phase shift, eventually deteriorating the optical sectioned image.